An oxygen generating electrode

Abstract

An electrode suitable for the oxygen evolution reaction of water electrolysis under alkaline conditions, comprising a ceramic material having a stability factor (SF) between 1.67 < SF < 2.8, calculated by formula (II), wherein r o represents the ionic radius of the oxide ion (O 2‑ ), r B,av represents the weighted average ionic radius of the transition metal, n A,Av represents the weighted average oxidation state of the rare earth metal or alkaline earth metal, r A,av represents the weighted average ionic radius of the rare earth metal or alkaline earth metal. The invention further relates to an alkaline electrolysis stack comprising at least one such electrode, and a method for water electrolysis using the alkaline electrolysis stack.

Description

Technical Field

[0001] This invention relates to an electrode for electrolysis, particularly an electrode suitable for oxygen generation in water electrolysis under alkaline conditions, which has a low overpotential in the oxygen evolution reaction. The invention also relates to an alkaline electrolytic reactor comprising at least one such electrode, and a method for water electrolysis using the alkaline electrolytic reactor under alkaline conditions. Background Technology

[0002] In alkaline water electrolysis, water is electrochemically converted into hydrogen and oxygen under alkaline conditions: H₂O = H₂ + 0.5O₂. The electrolytic cell contains two electrodes: an anode and a cathode. During operation, a potential is applied between the two electrodes, causing an electrolytic current to flow in the cell. During operation, hydrogen gas is generated at the cathode by the hydrogen evolution reaction (HER): 2H₂O + 2e⁻. - =H2 + 2OH - Oxygen is generated at the anode by the oxygen evolution reaction (OER): 2OH- - =0.5O2 + H2O + 2e - The alkaline electrolytic cell also includes an electrolyte comprising a liquid alkaline medium, such as an aqueous solution of hydroxides and / or carbonates. The electrolytic cell also includes a porous membrane and / or ion-exchange membrane capable of conducting hydroxide ions.

[0003] In alkaline water electrolysis, ideally, both the initial investment cost and energy consumption of the electrolyzer are minimized. All other things being equal, lower initial investment costs and energy consumption lead to lower hydrogen production costs. The initial investment cost of the electrolyzer is minimized when low-cost materials are used and the electrolyzers are produced using low-cost methods. Energy consumption is also minimized when the required applied potential (voltage) is minimized for a fixed operating current or current density.

[0004] The required applied potential is the sum of several potentials, including: 1) the theoretical potential required for the electrochemical reaction; 2) the potential generated due to the porous membrane and / or ion exchange membrane; 3) the overpotential induced by the anode; 4) the overpotential induced by the cathode; and 5) the potential related to the distance between the anode and cathode in the electrolytic cell. Here, the term "overpotential" refers to the difference between the theoretical and actual potentials applied to each electrode, including, for example, the potential caused by the formation of bubbles. Those skilled in the art will know that the overpotential of the anode (OER electrode) is typically higher than that of the cathode (HER electrode). Therefore, developing improved oxygen generation electrodes is crucial. In particular, these electrodes should be made from low-cost materials and manufactured using low-cost methods, while exhibiting lower overpotentials in OER than existing electrodes.

[0005] In industrial alkaline electrolyzers, OER electrodes are typically made of nickel or noble metals. Nickel-based electrodes are relatively inexpensive, but their high overpotential leads to high energy consumption in the electrolyzer, resulting in high hydrogen production costs. Conversely, electrodes based on noble metals or their compounds (such as IrO2, RuO2, and Pt) have lower overpotentials, but their high initial investment costs also contribute to high hydrogen production costs. A third class of alkaline electrolysis OER electrode materials has been discovered and demonstrated to exhibit low overpotentials while maintaining low cost. Specifically, ceramic materials with specific crystal structures, such as perovskite structures, have proven to be particularly attractive alternatives to nickel and noble metals in the manufacture of OER electrodes.

[0006] The formula for this type of ceramic material is described in WO 2013 / 012965 A1, filed by MIT and published on January 24, 2013. An OER catalyst is disclosed in the paper, with the formula A. x A' 1-x B y B' 1-y O 3±δ Where A and A' are each a rare earth metal or an alkaline earth metal, x ranges from 0 to 1, B and B' are each a transition metal, y ranges from 0 to 1, and δ ranges from 0 to 1. Example materials described in the cited application include LaCrO3, LaMnO3, LaFeO3, LaCoO3, LaNiO3, and LaNi. 0.5 Mn 0.5 O3, LaCu 0.5 Mn 0.5 O3, La 0.5 Ca 0.5 MnO 3-δ La 0.5 Ca 0.5 FeO 3-δLa 0.75 Ca 0.25 FeO 3-δ La 0.5 Ca 0.5 CoO 3-δ LaMnO 3-δ and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ The number of materials that can be described by the above expression is actually infinite, although the composition of some materials is described as A. x A' 1- x B y B' 1-y O 3±δ However, it is less suitable for use in alkaline electrolytic cells than other materials. Although the entire formula A... x A' 1-x B y B' 1-y O 3±δ It is stated that, however, when the occupancy rates of the σ-bond orbitals with eg symmetry in B and B', or for each element in B and B', are within a specific range, it leads to high activity of the OER. More specifically, Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ It was found to have exceptionally high OER activity: in 0.1M KOH, with an electrode overpotential of 0.4V, the OER current was 100 mA / cm. 2 In contrast, the OER currents of IrO2 and RuO2 electrodes under the same conditions were 18 mA / cm. 2 and 5mA / cm 2 .

[0007] The method proposed in WO 2013 / 012965 A1 primarily addresses the issue of insufficient stability of the claimed materials under conditions of use in industrial alkaline water electrolysis cells. The authors of WO 2013 / 012965 A1 subsequently demonstrated that, during OER in 0.1 M KOH solution, the material with the highest electrocatalytic activity among the mentioned materials, having lost its crystal structure, is Ba. 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ and SrCo 0.8 Fe 0.2 O 3-δHowever, some other materials, particularly LaCoO3, do not lose their crystal structure (cited in Journal: J. Phys. Chem. C, 117(2013) 8628, authors Risch et al.). Generally speaking, the loss of crystal structure or selective leaching of elements in a material implies a decrease in OER activity (i.e., an increase in overpotential).

[0008] US Patent 2016 / 0289850A1, filed by DE NORA TECH INC. and published on October 6, 2016, describes the operating conditions for an industrial alkaline water electrolyzer: preheating 5–30 wt% of the alkaline electrolyte KOH or NaOH (e.g., 25 wt% KOH) to 80°C. Therefore, achieving material stability under industrial conditions is more challenging compared to a 1M KOH solution at room temperature. At high temperatures (e.g., 80°C), using a concentrated alkaline solution (e.g., 25 wt% KOH) further reduces the applied potential required for this industrial alkaline water electrolyzer. The use of high temperature and high alkali concentration not only positively impacts the anode potential but also improves the potential due to the porous membrane and / or ion exchange membrane (increased conductivity of the membrane and / or diaphragm), the cathode overpotential, and the potential related to the distance between the anode and cathode (increased electrolyte conductivity leading to a lower ohmic drop). Therefore, as described in WO 2013 / 012965A1, although using a lower concentration of alkaline solution at a lower temperature may be more advantageous for the anode from a stability perspective, the improvement in anode performance usually cannot compensate for the performance degradation of other components of the electrolyzer caused by the lower temperature and lower alkaline concentration.

[0009] Therefore, there is still a need to find new ceramic materials that are low-cost, can generate low OER overpotentials, and can remain stable under industrial conditions (i.e., high temperature and concentrated alkaline solutions). Summary of the Invention

[0010] The inventors aimed to produce low-cost hydrogen through alkaline water electrolysis. They discovered that existing ceramic-based anodes still have shortcomings. More specifically, the anodes initially exhibit the lowest OER overpotential, for example, those containing Ba. 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ Anodes that do not deactivate under industrial electrolysis conditions often deactivate rapidly due to insufficient phase stability. On the other hand, anodes that do not deactivate under industrial electrolysis conditions typically exhibit extremely high OER overpotentials. Currently, the search for anode materials that do not deactivate but exhibit low OER overpotentials relies mainly on intuition and trial and error.

[0011] The inventors discovered a parameter called the "stability factor" (SF) that can successfully predict the phase stability of ceramic materials suitable for anodes in alkaline electrolytic cells. More specifically, based on the SF value, the stability of certain ceramic materials in strongly alkaline solutions and their OER activity (activity is inversely proportional to overpotential) can be estimated. Therefore, materials can be classified into the following types: a) highly active but phase-unstable materials, b) phase-stable but inactive materials, and c) both active and phase-stable materials. Highly active but phase-unstable materials have relatively high SF values, while phase-stable but inactive materials have relatively low SF values. Materials with intermediate SF values ​​exhibit both sufficient electrochemical activity (i.e., low OER electrode overpotential) and sufficient phase stability.

[0012] According to one aspect of the present invention, an electrode is provided for carrying out an electrochemical oxygen desorption reaction of water under alkaline conditions, the electrode comprising a ceramic material [(A x )A' (1-x) ] y B z B' (1-z) O 3-δ In this system, each A and A' is a rare earth metal or an alkaline earth metal, x ranges from 0 to 1, y is the A site occupancy rate ranging from 0.5 to 0.99, each B and B' is a transition metal, z ranges from 0 to 1, O is oxygen, δ is the oxygen non-stoichiometry, ranging from -1 to 1, and the SF of the ceramic material is greater than or equal to 1.67 and less than or equal to 2.8.

[0013] In the context of this invention, "stability coefficient" or "SF" refers to a parameter defined as:

[0014]

[0015] Where, r O It is oxygen ion (O 2 -) ionic radius, r B,av It is the weighted average ionic radius of B and B', n A,Av It is the weighted average oxidation state of A and A', and r A,av It is the weighted average ionic radius of A and A'.

[0016] The terms "phase stability" and "phase stability" refer to the property of a material to retain its crystalline phase when exposed to industrially relevant alkaline water electrolysis conditions. One way to assess the phase stability of a material, or whether it is phase-stable, is to obtain X-ray diffraction patterns of the material before and after exposure to these conditions. If there is no significant difference in the corresponding X-ray diffraction patterns, phase stability is confirmed, meaning that no phase transition has occurred in the bulk phase of the material. In the context of this invention, "industrially relevant alkaline water electrolysis conditions" refers to exposure to an aqueous solution of KOH at a temperature between 75 and 85 degrees Celsius, with a weight percentage exceeding 20%, regardless of whether an electrolytic current is applied. To verify phase stability, the exposure time should be at least 24 hours, preferably at least 100 hours. Of course, other alternative methods exist for determining phase stability; however, it should be noted that, in the context of this invention, surface-sensitive methods such as X-ray photoelectron spectroscopy or low-energy ion scattering are unsuitable for determining phase stability because these methods cannot detect the bulk phase of the material.

[0017] In the formula of this invention, "y" represents "A-site occupancy rate," which refers to the number of A-site cations relative to the number of B-site cations in the ceramic material. For example, in Ba... 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (It can also be written as [Ba) 0.5 Sr 0.5 ] 1.0 Co 0.8 Fe 0.2 O 3-δ In ), y = 1.0. In La... 0.95 CoO3 (also written as [La]) 1.0 ] 0.95 In CoO3), y = 0.95. Note that when estimating the occupancy of site A, the occupancy of site B is considered to be equal to 1. For example, to calculate LaCo 1.05 O 3.16 The occupancy rate of the A site, the material composition is expressed such that the subscript of the B-site cation (i.e., Co) is equal to 1, thus yielding La 0.95 CoO3, therefore y = 0.95.

[0018] The terms "A-site" and "B-site" refer to sites with different energies within the crystal lattice of a ceramic material. It is important to note that although the formula [(A... x )A' (1-x) ] y B z B' (1-z) O 3-δThis usually refers to materials with a perovskite structure (ABO3) or a double perovskite structure (A2B2O5), but in the context of this invention, the terms "A site" and "B site" are used more broadly and are unrelated to the crystal structure of ceramic materials.

[0019] In the formula of this invention, "δ" represents the "oxygen non-stoichiometry," which refers to the number of oxygen vacancies relative to B-site cations in the ceramic material. For example, for La... 0.90 Ni 0.6 Fe 0.4 O 2.85 (It can also be written as La) 0.90 Ni 0.6 Fe 0.4 O 3-0.15 ), δ = 0.15. In compounds with excess oxygen, the δ value is negative: for example, in La 0.3 Sr 0.7 TiO 3.15 (It can also be written as La) 0.3 Sr 0.7 TiO 3+0.15 In this case, δ = -0.15. Note that under the premise that δ' = 1-2δ, any double perovskite A2B2O 5+δ It can be represented as ABO 3-δ The non-stoichiometric ratio of oxygen depends on factors such as temperature, oxygen partial pressure, and applied voltage.

[0020] As defined by R.S. Shannon in Acta Crystallogr. A, 32 (1976) 751-767, "ionic radius" refers to the Shannon ionic radius. For example, the oxygen anion O 2- The ionic radius at a coordination number of 2 is In the context of this invention, "weighted average ionic radius of A and A'" refers to the ionic radius that satisfies the formula [(A x )A' (1-x) ] y B z B' (1-z) O 3-δ The weighted average of the Sanon ionic radii of cations A and A' in the ceramic material is calculated, where the weight of the ionic radius of A is x and the weight of the ionic radius of A' is (1-x). Then, the weighted average of the obtained radii is multiplied by the A-site occupancy rate y to obtain the following formula:

[0021]

[0022] “r A "r" refers to the ionic radius of A. A' "" refers to the ionic radius of A', obtained by the following formula:

[0023] r B,Av =z·r B +(1-z)·r B′

[0024] "Weighted average oxidation state" refers to the state that satisfies the formula [(A x )A' (1-x) ] y B z B' (1-z) O 3-δ In ceramic materials, the weighted average of the oxidation states of cations A and A' is calculated, where the weight of the oxidation state of A is x and the weight of the oxidation state of A' is (1-x). Then, the weighted average of the oxidation states is multiplied by the A-site occupancy rate y to obtain the following formula:

[0025]

[0026] Where n A It is the oxidation state of A, n A' It is the oxidation state of A'.

[0027] An "alkaline electrolytic reactor" refers to a device containing multiple electrically connected alkaline electrolytic cells. The more cells in the reactor, the more hydrogen and oxygen can be produced per unit time. Similarly, the larger the surface area (footprint) of each cell in the reactor, the more hydrogen and oxygen can be produced. The electrodes of the electrolytic cells in the reactor are separated by porous separators (such as Zirfon) and / or ion exchange membranes capable of conducting hydroxide ions.

[0028] The embodiments of the present invention have several important advantages compared with the prior art. First, the electrode of the present invention has sufficient phase stability, which means that frequent electrode replacement is not required during operation. Second, the electrode of the present invention has sufficient activity, enabling it to achieve low overpotential and high efficiency, thereby reducing the cost of hydrogen production. Third, the electrode of the present invention does not contain precious metals such as iridium, platinum, and ruthenium, thus solving the problem of difficult access to electrode materials and significantly reducing the cost of electrode raw materials. Fourth, the overpotential of the electrode of the present invention in the oxygen evolution reaction is lower than that of conventional nickel-based electrodes. Since electricity cost is the main factor determining the cost of hydrogen production by electrolysis, the electrode of the present invention makes the hydrogen production cost (operating cost) lower than that of conventional nickel-based electrodes.

[0029] EP3587622 A1, filed by Japanese company Asahi Kasei Kabushiki Kaisha and published on January 1, 2020, describes an anode for water electrolysis, comprising a porous substrate and a metal oxide layer. The surface of the metal oxide layer contains at least one perovskite-structured metal oxide, and the perovskite-structured metal oxide constitutes 90% or more but not more than 100% of the crystal composition of the metal oxide layer. EP 3587622 A1 also describes an anode in which the composition of the perovskite-structured metal oxide can be represented as A. x A' (1-x) Ni y B' (1-y) O 3-z Where A and A' are alkaline earth metals or rare earth elements, B' is Cr, Mn, Fe, Co, or Cu, x satisfies 0 ≤ x ≤ 1, y satisfies 0 ≤ y ≤ 1, and z satisfies 0 ≤ z ≤ 1. EP3587622A1 records the value after 100 hours, or at 6 kA / m 2 Determine the overvoltage value for operation and confirm Ba. 0.5 Sr 0.5 Co 0.8 FeO3 performs worse than LaNiO3 (possibly due to poor phase stability). Ba 0.5 Sr 0.5 Co 0.8 The SF value of FeO3 is 3.91, while that of LaNiO3 is 1.62. This indicates that Ba... 0.5 Sr 0.5 Co 0.8 FeO3 exhibits insufficient long-term stability under industrial conditions, while LaNiO3 has excessively low oxygen evolution reaction (OER) activity, and its associated overpotential can be further reduced by increasing the A-site occupancy rate (0.5≤y≤0.99). Furthermore, the method of coating perovskite onto a nickel substrate is labor-intensive, requiring 13 coating and drying cycles followed by a calcination cycle.

[0030] Ma et al. published a series of perovskite oxides in the Journal of Alloy and Compounds, 854(2021)157154: La 0.95 FeO3, La 0.95 Fe 0.9 Co 0.1 O3, La 0.95 Fe 0.8 Co 0.2 O3, La 0.95 Fe 0.7 Co 0.3 O3 and La 0.95 Fe0.6 Co 0.4 O3. Of these five materials, Ma et al. did not further explain La. 0.95 FeO3 and La 0.95 Fe 0.6 Co 0.4 O3, focusing on the other three materials: La 0.95 Fe 0.9 Co 0.1 O3, La 0.95 Fe 0.8 Co 0.2 O3, La 0.95 Fe 0.7 Co 0.3 O3. The authors then subjected these three materials to reduction treatment to induce the precipitation of Co or Co / Fe nanoparticles, and then evaluated the OER performance of these materials. Importantly, the composition of the original materials inevitably changes during the reduction process. For example, La 0.95 Fe 0.9 Co 0.1 O3 is converted to LaFe 0.9 Co 0.1 O3 and Fe0.9Co0.1 (per mole of La) 0.95 Fe 0.9 Co 0.1 O3 contains 0.95 moles of LaFe 0.9 Co 0.1 O3 and 0.05 mol Fe0.9Co0.1). In all cases, the resulting material is no longer A-site deficient. LaFe 0.9 Co 0.1 O3, La 0.95 Fe 0.8 Co 0.2 O3 and La 0.95 Fe 0.7 Co 0.3 The stability coefficients of O3 were calculated to be 1.65, 1.65, and 1.66, respectively. The difference between this invention and the document in this paper is that the material of this invention does not suffer from a deficiency or loss of A-site ions due to the reduction reaction.

[0031] Poznyak et al. disclosed a series of perovskite materials in the Journal of Solid State Electrochemistry 12 (2008) 15-30: La 0.3 Sr 0.7 CoO 2.924 La 0.3 Sr 0.7 Co 0.8 Al 0.2 O 2.85 、(La0.3 Sr 0.7 ) 0.97 CoO 2.896 La 0.5 Sr 0.5 CoO3, La 0.55 Sr 0.45 CoO3, La 0.65 Sr 0.35 CoO3, La 0.7 Sr 0.3 CoO3, La2NiO 4.15 La2Ni 0.9 Co 0.1 O 4.169 La2Ni 0.8 Cu 0.2 O 4.124 Although some of these materials have a perovskite structure, one material has an A-site occupancy of less than 1, and some materials have an SF of less than 2.8; therefore, no material in the literature simultaneously satisfies all three conditions. Thus, this invention is distinguishable from the prior art.

[0032] According to one aspect of the invention, the electrode further includes a second material, which is metallic nickel, a metallic alloy of nickel and iron, or a hydroxide of nickel and iron. One advantage of combining the ceramic material with the second material, rather than with conventional electrode materials, is that the second material can provide partial electrochemical activity to the combined electrode. This is particularly important when the electrode is partially contaminated by impurities: if the electrode is made of multiple materials, these materials have different affinities for different impurities, i.e., they are affected by impurity adsorption to varying degrees. Therefore, electrodes containing multiple materials are generally more stable and durable than electrodes containing only a single material. Note that the second material can be incorporated before or after exposure to operating conditions. For example, it is known that iron impurities in the electrolyte may deposit on the electrode during operation.

[0033] DE NORA PERMELEC LTD of Japan, in its patent application EP3444383B1 published on February 20, 2019, describes an anode for alkaline water electrolysis, comprising a conductive substrate at least composed of nickel or a nickel-based alloy, and an electrode catalyst layer formed on the surface of the conductive substrate. The catalyst components constituting the electrode catalyst layer include: a first catalyst comprising: a nickel-cobalt spinel oxide with the structural formula NiCo2O4, or a nickel-cobalt spinel oxide with the structural formula XNiCo2O4. 1- aLanthanide metal-nickel-cobalt perovskite oxides of O3 (where X represents at least one metal selected from lanthanide elements such as lanthanum, cerium, and praseodymium, and 0 < a < 1); and a second catalyst, the composition of which contains at least one iridium oxide and ruthenium oxide, where the amount of the second catalyst composition (calculated in terms of the amount of the metal component) is at least 0.2 g / m 2 . The perovskite materials described in EP 3444383 B1 generally exhibit very low SF values. For example, for all LaNiaCo 1-a O3 compositions, SF < 1.67: for example, LaNi 0.1 Co 0.9 O3 (SF = 1.66), LaNi 0.5 Co 0.5 O3 (SF = 1.64), LaNi 0.9 Co 0.1 O3 (SF = 1.63). In other words, the materials selected here are not ideal for OER: they are "too stable", and more active materials can be obtained by adjusting the A-site occupancy rate within the range of 0.5 to 0.99. In addition, the electrodes described in EP 3444383 B1 still contain a large amount of iridium and ruthenium oxides to achieve the required activity level. Due to the very limited content of these elements in the earth's crust, resulting in high costs, the use of iridium and ruthenium is problematic.

[0034] According to an embodiment of the present invention, the ceramic material is uniformly dispersed on the surface of the second material. "X is uniformly dispersed on the surface of Y" means that on the premise that the inspection area is large enough, no matter which part of Y is inspected, the concentration of X particles on the surface of Y is the same. For example, "X" refers to the ceramic material and "Y" refers to the second material. In the context of the present invention, if the inspection area contains at least 500 X particles identified by an electron microscope, the inspection area is considered to be large enough. The advantage of dispersing the ceramic material on the surface of the second material is to obtain an electrode with uniform electrochemical activity. In addition, since the electrochemical reaction on the surface of the electrode material is related to a significant reaction enthalpy, the uniform dispersion of the ceramic material helps to avoid "hot spots" (local temperature gradients) in the electrode, which may damage the electrode structure or the separator membrane.

[0035] According to one aspect of the invention, particles of ceramic material are fixed and partially coated by a second material. In the context of this invention, "X is fixed" means that the particles of X cannot detach and move during electrolytic cell operation. Furthermore, "X is partially coated by Y" means that the contact between the particles of X and Y is from multiple sides (partial coating), rather than all sides (complete coating). The advantage of this aspect is that the ceramic material is firmly locked in during operation, thereby avoiding, for example, uneven electrode activity or mechanical problems caused by ceramic particles falling to the bottom due to gravity. Partial coating is a particularly effective method for dispersing ceramic material on the surface of a second material because it ensures that the ceramic material adheres firmly to the surface of the second material while still being exposed to the electrolyte, thus maintaining electrochemical activity.

[0036] According to one aspect of the invention, A is an element from the following list of elements: La (lanthanum), Ce (cerium), Gd (gadolinium), Pr (europium), Ba (barium); A' is an element from the following list of elements: Sr (strontium), Ca (calcium), Ba (barium), Ce (cerium); and B or B' is each an element from the following list of elements: Mn (manganese), Ni (nickel), Fe (iron), Co (cobalt), Ti (titanium), Cr (chromium). The advantage of choosing La, Ce, Gd, Pr, or Ba as A is that they have suitable cation sizes (La...) in the perovskite lattice. 3+ Ce 3+ Gd 3+ Pr 3+ and Ba 2+ ), and the availability (price) of these elements. For example, from the perspective of ionic radius, Dy 3+ and Eu 3+ It is also suitable, but its high price prevents its widespread use. The advantage of choosing Sr, Ca, Ba, or Ce as A' is that these elements typically improve the electrical conductivity and oxygen vacancy concentration of ceramic materials. The advantages of choosing Mn, Ni, Fe, Co, Ti, or Cr as B or B' are twofold: First, the use of transition metals improves the electronic conductivity of the material because these metals have multiple possible oxidation states, thus enabling mechanisms such as polaron hopping conduction. Second, since Mn, Ni, Fe, Co, Ti, or Cr are less expensive than Ru or Ir, using Mn, Ni, Fe, Co, Ti, or Cr as B or B' is superior to using metals such as Ru or Ir as B or B'.

[0037] According to one embodiment of the invention, the A-site occupancy, denoted as y, is in the range of 0.6 to 0.98, preferably in the range of 0.75 to 0.98. A-site occupancy below a single-unit value (e.g., 0.9) is advantageous because it allows for a tighter bond between the A-site cation and the crystal structure. However, when the A-site occupancy is too low (e.g., below 0.6), some B-site cations may not be able to embed themselves in the ceramic material structure, resulting in some B-cations forming a secondary oxide phase. An optimal range of A-site occupancy yields the best results, for example, between 0.6 and 0.98, preferably between 0.75 and 0.98.

[0038] According to one embodiment of the invention, the average particle size of the ceramic material is between 10 nm and 300 nm, preferably between 20 nm and 200 nm. Generally, the electrochemical and catalytic activity of a material increases with increasing surface area. Therefore, maximizing the surface area of ​​the ceramic material, i.e., reducing the average particle size, is desirable. However, once the particle size becomes too small, for example below 20 nm, the material properties begin to change because more material atoms now occupy the edges and corners of the particles. This phenomenon affects not only the electrochemical activity of the material but also its stability, typically leading to decreased stability. Therefore, the average particle size of the ceramic material should be within an optimal range, for example, between 10 nm and 300 nm or between 20 nm and 200 nm.

[0039] According to one aspect of the invention, the ceramic material has a perovskite crystal structure. Because the perovskite structure is a highly versatile material, it is generally more stable than the corresponding Ruddlesden-Popper phase (e.g., less sensitive to A-site cation leaching), exhibiting superior properties. Perovskite typically possesses higher electrochemical activity than the corresponding spinel phase.

[0040] According to one embodiment of the present invention, when an oxygen evolution reaction is carried out using a rotating disk electrode in 20% to 35% KOH at a temperature of 75 to 85 degrees Celsius at a rotation speed of 1500 rpm, the current density is 1 mA / cm². 2 At this time, the overpotential of the electrode should be less than or equal to 400 millivolts. The electrode of this invention is optimized for industrial alkaline electrolysis conditions, i.e., KOH weight percentage of 20% to 35% and temperature range of 75°C to 85°C. The overpotential of the electrode in the oxygen evolution reaction is minimized, at an electrolysis current density of 1 mA / cm². 2At this stage, the overpotential should be less than or equal to 400 mV to at least achieve performance comparable to state-of-the-art iridium-based electrodes. In typical rotating disk electrode experiments, ceramic material is deposited onto the electrode surface (e.g., glassy carbon electrode) and immersed in a KOH solution. Electrode performance (overvoltage at different current densities) can be evaluated at a range of electrode rotation speeds to investigate the effects of kinetics and mass transport limitations. Ohmic losses can be corrected by additional electrochemical impedance spectroscopy measurements.

[0041] According to one embodiment of the invention, the ceramic material exhibits phase stability for 100 hours in 6M KOH at 80°C. The typical lifespan of an alkaline electrolytic cell is approximately 10 years, and all materials used in such cells must be able to withstand the operating conditions throughout the entire lifespan of the electrolytic cell. However, to screen materials for use in alkaline electrolytic cells, exposure to 6M KOH at 80°C for 100 hours is generally sufficient to assess the phase stability of the material. Materials that fail to maintain phase stability after 100 hours of exposure to 6M KOH at 80°C are unsuitable for use as electrode materials. Attached Figure Description

[0042] Figure 1 This is a schematic diagram showing the relationship between the stability and activity of ceramic materials and their stability coefficient. Detailed Implementation

[0043] Appendix Figure 1 a shows the qualitative relationship (in arbitrary units) between the phase stability (stability (au)) represented by the left vertical axis and the stability coefficient (SF) represented by the horizontal axis. Specifically, when the SF value is low, the formula [(Ax)A'( 1-x )] y B z B' (1-z) O 3-δ The phase stability of ceramic materials increases, meaning they are less prone to decomposition and phase transitions under electrolytic conditions. However, the phase stability decreases with higher SF values; when SF > 2.8, these materials lose phase stability under industrially relevant electrolytic conditions. Therefore, materials with SF > 2.8 are not particularly suitable for use as oxygen electrodes in alkaline electrolytic cells.

[0044] In addition, Figure 1 a also shows the qualitative relationship (in arbitrary units) between the electrochemical activity (activity (au)) represented by the right vertical axis and the stability coefficient (SF) represented by the horizontal axis. Specifically, when the SF value is high, the formula [(Ax)A'( 1-x )] y B z B' (1-z) O 3-δThe electrochemical activity of ceramic materials increases, meaning that the overpotential of the oxygen evolution reaction (OER) decreases when these materials are exposed to electrolytic conditions. The activity of such materials decreases at lower SF values, and when SF < 1.67, these materials are no longer sufficiently active under industrially relevant electrolytic conditions. Therefore, materials with SF < 1.67 are not particularly suitable for use as oxygen electrodes in alkaline electrolytic cells.

[0045] Appendix Figure 1 b shows the qualitative relationship (in arbitrary units) between the parameter "stability multiplied by activity" on the vertical axis and the stability coefficient (SF) on the horizontal axis. When 1.67 ≤ SF ≤ 2.8, the optimal performance material is obtained, that is, the material has both high stability and high activity.

[0046] Best way to carry out the invention

[0047] The method is illustrated in more detail in the following non-restrictive examples.

[0048] Example 1 (Comparison Example)

[0049] Table 1 lists some of the relevant material properties and SF values ​​of barium strontium cobalt ferrite ceramic materials. 2+ At a coordination number of 12, the radius of the Shannon ion is... And Sr 2+ At a coordination number of 9, the ionic radius is Therefore, we obtain Co 3+ At a coordination number of 6, the radius of the Sanon ion is Fe 3+ At a coordination number of 6, the ionic radius is Table 1 provides the corresponding r. B,av Value. Regardless of the Co:Fe ratio, y=1 (Ba 0.5 Sr 0.5 ) 1.0 Co z Fe 1-z O 2.5 The SF value of the material remains almost constant. For example, Ba with y=1 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 2.5 The SF value is 3.50, Ba 0.5 Sr 0.5 Co 0.2 Fe 0.8 The SF value of O3 is 3.49. In other words, regardless of (Ba 0.5 Sr 0.5 ) 1.0 Coz Fe 1-z The choice of Co:Fe ratio in O3 determines whether the material will exhibit phase stability under conditions related to industrial alkaline electrolysis. This is consistent with the predicted results. 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ It is unstable in 0.1M KOH.

[0050] The materials in Table 1 can be synthesized using (but not limited to) solid-state synthesis, co-precipitation, hydrothermal synthesis, sol-gel synthesis, chemical vapor deposition, spray pyrolysis, atmospheric plasma deposition, etc., by mixing metal precursors in the desired proportions and optionally treating the resulting mixture to form the correct crystalline phase. The same methods can also be used to synthesize the materials described in the examples below.

[0051] Table 1

[0052]

[0053] Example 2 (Comparison Example)

[0054] Table 2 lists some relevant material properties and SF values ​​of barium strontium cobalt ferrite ceramic materials. In Table 2, (Ba 0.5 Sr 0.5 ) y Co 0.8 Fe 0.2 O 3-δ The A-site occupancy rate y of the material systematically varies within the range of 0.7 ≤ y ≤ 1. As the value of y decreases, the SF value increases, indicating a decrease in the phase stability of the material. Regardless of the (Ba) site occupancy rate... 0.5 Sr 0.5 ) y Co 0.8 Fe 0.2 O 3-δ The value of y is chosen to predict whether the material will have phase stability under conditions related to industrial alkaline electrolysis.

[0055] Table 2

[0056]

[0057] Example 3 (Comparison Example)

[0058] Table 3 lists some relevant material properties and SF values ​​of barium strontium cobalt ferrite ceramic materials. In Table 3, (Ba x Sr 1-x ) 1.0 Co 0.8 Fe 0.2 O2.5 The Ba:Sr ratio x of the material varies systematically within the range of 0.1 ≤ x ≤ 0.9. Regardless of the Ba:Sr content... x Sr 1-x ) 1.0 Co 0.8 Fe 0.2 O 2.5 The value of x is chosen to predict whether the material will have phase stability under industrial alkaline electrolysis conditions.

[0059] Table 3

[0060]

[0061] Example 4 (Comparison Example)

[0062] Table 4 lists some (A) 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 The relevant material properties and SF values ​​of O3 family ceramic materials are shown in Table 4. (The table is derived from Ba...) 2+ Ce 3+ Gd 3+ Pr 3+ and La 3+ Choose different A, one element in the A-position cation, (A) 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 3-δ Systemic changes in A within Ba. 2+ At a coordination number of 12, the radius of the Sanon ion is And Sr 2+ At a coordination number of 9, the ionic radius is Get (Ba 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.5 of La 3+ At a coordination number of 12, the radius of the Sanon ion is (12 coordination), yielding (La) 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.75 of Ce 3+ (12-coordinated), Pr 3+(9-coordinated) and Gd 3+ The radii of the (8-coordinated) Sanon ion are respectively and Obtain material (Gd) 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.75 、(Pr 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.75 、(La 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.75 and (Ce 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.75 The SF values ​​were all below 3.1, while (Ba 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 2.5 SF = 3.5. Therefore, it is expected that in material (A) 0.5 Sr 0.5 ) 1.0 Co 0.8 Fe 0.2 O 3-δ In this study, materials with Ce, Gd, Pr, and La as A are more stable than those with Ba as A, but these materials are not stable enough and are not suitable for use in industrial alkaline electrolysis cells.

[0063] Table 4

[0064]

[0065]

[0066] Example 5

[0067] Table 5 lists some relevant material properties and SF values ​​of gadolinium-strontium-cobalt ferrite ceramic materials. In Table 5, (Gd x Sr 1-x ) 0.97 Co 0.8 Fe 0.2 O 3-δThe Gd:Sr ratio x of the material systematically varies within the range of 0.1 ≤ x ≤ 0.9. Compared to the control example in Example 3, the two A-site cations carry different positive charges (Gd... 3+ and Sr 2+ This leads to better phase stability at high Gd content: materials with x < 0.2 have an SF value below 2.8, and are therefore expected to be phase stable under industrial alkaline electrolysis conditions. Materials with 0.2 ≤ x ≤ 1 in Table 5 do not exhibit phase stability.

[0068] Table 5

[0069]

[0070] Example 6

[0071] Table 6 lists some (La) 0.6 A' 0.4 ) 0.99 Co 0.8 Fe 0.2 O 3-δ The relevant material properties and SF values ​​of the family's ceramic materials. Ca 2+ The radius of the Sanon ion at a coordination number of 12 is Sr 2+ The ionic radius at a coordination number of 9 is Ba 2+ The ionic radius at a coordination number of 12 is And Ce 3+ The ionic radius at a coordination number of 12 is In Table 6, the A-site cation A' is located in (La 0.6 A' 0.4 ) 0.99 Co 0.8 Fe 0.2 O3 represents a systematic change, and A' is selected from Sr. 2 + Ca 2+ Ba 2+ and Ce 3+ In Table 6, the SF values ​​of all materials are in the range of 1.67≤SF≤2.8, but the SF values ​​of any material are in the range of 1.9≤SF≤2.6.

[0072] Table 6

[0073]

[0074] Example 7

[0075] Table 7 lists some (La) 0.9 Sr 0.1 ) 0.97 BO 3-δThe relevant material properties and SF values ​​of the ceramic materials of the group are listed in Table 7. The B-site cation B' in (La...) 0.9 Sr 0.1 ) 0.97 BO 3-δ The oxidation state of B' is a systematic variation, and B' is selected from Mn, Ni, Fe, Co, Ti, and Cr. It is assumed that the average oxidation state of Mn, Ni, Fe, Co, and Cr ions is 3.1. The exception is Ti, with Ti being the most common oxidation state. 4+ (6-coordinated) exists, and its ionic radius is We obtain δ = -0.455. Co 3+ Co 4+ Fe 3+ Fe 4+ Mn 3+ Mn 4+ Ni 3+ Ni 4+ Cr 3+ and Cr 4+ The ionic radii (both 6-coordinated) are respectively and The SF values ​​of all materials in Table 7 are within the range of 1.67 ≤ SF ≤ 2.8.

[0076] Table 7

[0077]

[0078] Example 8

[0079] Table 8 lists some (La) 0.9 Sr 0.1 ) y BO 3±δ The relevant material properties and SF values ​​of the family of ceramic materials. In Table 8, when 0.65 ≤ y ≤ 0.95 is determined, the B-site cation B' in (La 0.9 Sr 0.1 )yBO 3±δ The composition is a systematic change, with B' selected from Mn, Ni, Fe, Co, Ti, and Cr. It is assumed that the average charge of Mn, Ni, Fe, Co, and Cr ions is 3.1, while Ti is designated as Ti... 4+ Comparing the SF values ​​in Table 8 with those in Table 7, it is clear that reducing the A-site occupancy of ceramic materials can systematically increase the SF value; that is, by changing y, the activity and phase stability of the material can be adjusted. Some materials, such as (La... 0.9 Sr 0.1 ) 0.90 TiO 3.31 、(La 0.9 Sr 0.1 )0.8 TiO 3.16 、(La 0.9 Sr 0.1 ) 0.65 TiO 2.94 and(La 0.9 Sr 0.1 ) 0.90 CrO 2.86 It becomes too unstable (SF>2.8), while other materials remain relatively stable (1.67≤SF≤2.8).

[0080] Table 8

[0081]

[0082] Example 9

[0083] Table 9 lists some relevant material properties and SF values ​​of lanthanum nickelate-ferrite ceramic materials. For example, LaNi with y = 1 0.6 Fe 0.4 The SF value of O3 is 1.63, while the La value of y = 0.95 is... 0.95 Ni 0.6 Fe 0.4 O 2.925 The SF value is 2.10. La 0.90 Ni 0.6 Fe 0.4 O 2.85 The SF value is 2.55. In Table 9, the SF values ​​of materials with y ≤ 0.85 all exceed 2.8. LaNi with y = 1... 0.6 Fe 0.4 O3 remains phase stable when exposed to 6M KOH at 80°C, while materials with y ≤ 0.85 in Table 9 do not exhibit phase stability. In more extreme cases, such as La... 0.5 Ni 0.6 Fe 0.4 O 2.25 Ceramic materials do not form perovskite structures and exist as multiphase and multicomponent materials even before exposure to industrial alkaline electrolysis conditions. Conversely, when y = 1, LaNi... 0.6 Fe 0.4 O3 is not very active in the oxygen evolution reaction due to its very low SF value.

[0084] Table 9

[0085]

[0086]

[0087] Example 10

[0088] La 0.95CoO 2.925 Pr 0.95 CoO 2.925 Gd 0.95 CoO 2.925 、(La 0.9 Sr 0.1 ) 0.95 CoO 2.878 La 0.95 NiO 2.925 LaFeO 2.925 La 0.95 Ni 0.6 Co 0.4 O 2.925 and La 0.95 Ni 0.6 Fe 0.4 O 2.925 A modified sol-gel synthesis method was used to prepare the material. The obtained material was calcined at 800 °C for 3 hours to obtain an oxidation catalyst with a perovskite structure, which was verified by X-ray diffraction measurements. The material properties and SF values ​​are summarized in Table 10.

[0089] Table 10

[0090]

[0091] The calcined materials were electrochemically treated in a rotating disk electrode (RDE) setup. For this purpose, each perovskite material was mixed with Nafion solution, isopropanol, and ultrapure water to prepare a slurry, which was then loaded at a concentration of 0.2 mg / cm³. 2 The electrode was coated onto a glassy carbon electrode. A three-electrode test was performed in argon-saturated 0.1 M KOH. Oxygen evolution reaction (OER) kinetics were evaluated by applying a linearly varying voltage and measuring the corresponding current. The voltage potential was increased from 1.3 V to 1.9 V and then back to 1.3 V relative to a standard reversible hydrogen electrode (RHE). The electrode was rotated at 1500 rpm, and measurements were performed at room temperature.

[0092] In addition, the materials were treated with a strong alkali to assess phase stability. Each material was treated with 6M KOH at 80°C for 100–120 hours. After treatment, the materials were thoroughly rinsed with distilled water, dried, and their crystal structures were studied by X-ray diffraction (XRD).

[0093] Specifically, calcined Gd 0.95 CoO 2.925The material is primarily composed of perovskite, with main XRD peaks at 2θ angles of 33.86°, 34.36°, and 33.20° (in descending order of intensity). This material exhibits high electrochemical activity, reaching 10 mA / cm². 2 The required voltage for the OER current is 1.67V. Due to its high stability factor (SF>2.8), the material lacks phase stability after treatment with 6MKOH. The main XRD peak changes are at 2θ angles of 28.19°, 50.70°, 41.25°, and 29.52°, indicating that the original perovskite material has decomposed. The activity of the KOH-treated material in RDE measurements is significantly reduced (reaching 10 mA / cm). 2 The required voltage is 1.73V. Gd 0.95 CoO 2.925 This is an example showing that materials are initially very electrochemically active, but lack sufficient phase stability under industrially relevant alkaline electrolysis conditions.

[0094] Calcinated La 0.95 Ni 0.6 Fe 0.4 O 2.925 The material is primarily composed of perovskite, with main XRD peaks at 2θ angles of 32.56°, 32.84°, and 46.94° (in descending order of intensity). The material exhibits electrochemical activity, reaching 10 mA / cm². 2 The required voltage for the OER current is 1.66V. Based on its SF value (1.67≤SF≤2.8), the material exhibits phase stability after treatment with 6M KOH. The main XRD peaks remained unchanged at 2θ angles of 32.60°, 32.80°, and 46.98° (in descending order of intensity), indicating that the original perovskite material remained stable under these treatment conditions. The activity of the KOH-treated material was slightly reduced in RDE measurements, but still within acceptable limits (reaching 10 mA / cm). 2 The required voltage is 1.72V. 0.95 Ni 0.6 Fe 0.4 O 2.925 This is an example material that exhibits both good electrochemical activity and good phase stability under industrially relevant alkaline electrolysis conditions.

[0095] The calcined LaFeO3 material is mainly composed of perovskite, with main XRD peaks at 2θ angles of 33.16°, 57.40°, and 46.16° (in descending order of intensity). This material exhibits high electrochemical inactivity: at a voltage increased to 1.9V, the current density at 1.9V is only 3.5 mA / cm². 2 It failed to reach 10 mA / cm2 The OER current was measured. Based on its low SF value (SF < 1.67), the material exhibits phase stability after treatment with 6M KOH. The main XRD peaks remained unchanged, indicating that the original perovskite material had been decomposed. LaFeO3 is an example material that exhibits high stability under industrially relevant alkaline electrolysis conditions but lacks sufficient activity for OER.

[0096] An electrode suitable for the oxygen evolution reaction in alkaline water electrolysis can be designed by following these steps:

[0097] Step 1: Select the expression that satisfies [(A x )A' (1-x) ] y B z B' (1-z) O 3-δ Ceramic materials, such as LaNi 0.6 Fe 0.4 O3,

[0098] Step 2: Using the SF calculation formula, estimate the SF value based on the ionic radius, oxidation state, A-site percentage (y), oxygen nonstoichiometry (δ), and A-site and B-site doping levels (x and z, respectively). For example, for LaNi... 0.6 Fe 0.4 The SF value of O3 is 1.63.

[0099] Step 3: If SF is within a suitable range (1.67 ≤ SF ≤ 2.8), the material can be synthesized using (but not limited to) the method in Example 1, and further testing can be performed on selected ceramic materials. For example, the material can be exposed to 6M KOH at 80°C for 100 hours to verify phase stability. For example, since SF < 1.67, LaNi 0.6 Fe 0.4 O3 will not be selected for further testing.

[0100] Step 4: If SF is outside the appropriate range, adjust the y value to be within the range of 0.5 to 0.99, preferably within the range of 0.6 to 0.98, to change the SF value. For example, by changing the y value from 1.0 to 0.95 (from LaNi... 0.6 Fe 0.4 O3 changed to La 0.95 Ni 0.6 Fe 0.4 O 2.925 The SF value can be increased to 2.1, thus satisfying the condition: 1.67≤SF≤2.8.

[0101] Step 5: As an alternative to Step 4, the SF value can be changed by altering the values ​​of x and / or z. For example, by changing the value of z from 0.6 to 0.1 (from LaNi...).0.6 Fe 0.4 O3 changed to LaNi 0.1 Fe 0.9 O3 can increase the SF value from 1.63 to 1.65.

[0102] Step Six: As an alternative to Step Four or Five, the SF value can be altered by changing the elemental composition of the ceramic material. For example, this can be achieved by replacing Fe with Co, thus changing the material's composition from LaNi... 0.6 Fe 0.4 O3 changed to LaNi 0.6 Co 0.4 O3 can increase the SF value from 1.63 to 1.64.

[0103] Step Seven: Advantageously combine steps Four, Five, and Six. For example, by reducing y from 1 to 0.95, i.e. from LaNi 0.6 Co 0.4 O3 changed to La 0.95 Ni 0.6 Co 0.4 O 2.85 This can increase the SF value from 1.64 to 2.04, thus satisfying the condition 1.67≤SF≤2.8.

Claims

1. An electrode suitable for carrying out the water electrolysis oxygen reaction under alkaline conditions, characterized in that, The electrode comprises: a. Ceramic materials that satisfy formula (I): (I) Where A and A' are each a rare earth metal or an alkaline earth metal, x ranges from 0 to 1, y is the A site occupancy rate, ranging from 0.5 to 0.99, B and B' are each a transition metal, z ranges from 0 to 1, O is oxygen, and δ is the oxygen non-stoichiometry, ranging from -1 to 1; and b. A second material, wherein the second material is metallic nickel, iron and a metallic alloy of nickel or a hydroxide of nickel and iron; The stability factor (SF) of the ceramic material satisfies formula (II): (II) Where, r O For oxygen ions (O 2- The Shannon ion radius, r B,av The weighted average radii of the Sanon ions, B and B', satisfy formula (III): (III) Where, r B Let r be the radius of the Sanon ion of B. B' Let n be the ionic radius of B'. A,Av The weighted average oxidation states of A and A' satisfy formula (IV): and(IV) Where, n A Let n be the oxidation state of A. A' For A', the oxidation state is r. A,av The weighted average ionic radii of A and A' satisfy formula (V): y(V) Where, r A Let r be the radius of the Sanon ion of A. A' Let A' be the ionic radius. The properties of the ceramic material satisfy the following formula: A is an element in the following list: La, Ce, Gd, Pr, Ba; A' is an element in the following list: Sr, Ca, Ba, Ce; and B or B' is an element in the following list: Mn, Ni, Fe, Co, Ti, Cr.

2. The electrode as described in claim 1, characterized in that, The ceramic material satisfying formula (I) is uniformly dispersed on the surface of the second material.

3. The electrode as described in claim 1 or 2, characterized in that, The particles of the ceramic material are fixed and partially encapsulated in the second material.

4. The electrode as described in claim 1, characterized in that, y is in the range of 0.6 to 0.

98.

5. The electrode as described in claim 4, characterized in that, y is in the range of 0.75 to 0.

98.

6. The electrode as claimed in claim 1, characterized in that, The average particle size of the ceramic material satisfying formula (I) is between 10 nanometers and 300 nanometers.

7. The electrode as claimed in claim 6, characterized in that, The average particle size of the ceramic material satisfying formula (I) is between 20 nanometers and 200 nanometers.

8. The electrode as described in claim 3, characterized in that, The ceramic material that satisfies formula (I) has a perovskite crystal structure.

9. The electrode as claimed in claim 1, characterized in that, When the oxygen evolution reaction is carried out using a rotating disk electrode at a speed of 1500 rpm in 20-35% KOH at a temperature of 75 to 85 degrees Celsius, the overpotential of the electrode for the oxygen evolution reaction is less than or equal to 400 millivolts at a current density of 1 mA / cm².

10. The electrode as claimed in claim 1, characterized in that, The ceramic material satisfying formula (I) has a phase stability of 100 hours in 6 M KOH at 80 degrees Celsius.

11. The electrode as claimed in claim 9, characterized in that, 。 12. An alkaline electrolytic reactor, comprising at least one electrode as described in any of the preceding claims.

13. A method for water electrolysis under alkaline conditions using an alkaline electrolytic reactor according to claim 12.

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